Specificity and host predictability: a comparative analysis among monogenean parasites of fish

Abstract

1. This article compares generalist (parasite species found on two or more host species) and specialist (found on only one host species) monogenean parasite species of fish. The reduction of the host range – that is an increase in host specificity – may correspond with a better adaptation of the parasite to a more predictable host environment. A more predictable environment may allow the parasite species to develop specific adaptations. 2. We assume that the more predictable host environment can be evaluated by host body size, since numerous life‐traits, such as longevity, are positively correlated with size. 3. We found that specialist parasites parasitize larger hosts species than generalist parasites. We also found a good relationship between host body size and parasite body size for specialist parasite species. 4. An adaptation to the mechanical problems encountered in the host's gill chamber may lead to an increase in parasite body size. The infection of a larger part of the host population in order to decrease the chances of local extinction due to fluctuations of host abundance may be another adaptive mechanism. 5. We found a negative correlation between parasite body size and prevalence for generalist parasite species. This relationship disappeared when using the comparative method controlling for phylogeny, which proved that it was a phylogenetic effect.

Resource predictability and host specificity in fleas: the effect of host body mass

“…In general, small-bodied hosts harboured mainly hostopportunistic fleas (with a high number and/or low taxonomic 'evenness ' of exploited hosts), whereas host-specific fleas tend to use larger hosts. This finding supports the observations of Sasal et al (1999), Simkova et al (2001) and Desdevises et al (2002) for fish-monogenean systems and suggests some role for the predictability of resources in the evolution of flea host specificity. Indeed, large hosts live longer than smaller hosts and, thus, represent more permanent sources of food and living space for fleas.…”

Dynamics of a parasite assemblage of the Vermilion Rockfish Sebastes miniatus from northwestern Baja California, México

“…This could be because they find there a high availability of nutrients and low competition for resources (Stromnes and Andersen 1998). Thus, the specificity for certain microhabitats could also help determine the community structure of parasites in S. miniatus (Sasal et al 1999). This specificity for organ host was similar to those reported in S. capensis (from the southeastern Pacific) (González and Acuña 1998).…”

Sponge host characteristics shape the community structure of their shrimp associates

“…Certain types of species interactions are highly size-structured, including many mutualistic plant -pollinator relationships (Fenster et al 2004, Borrell 2005, Dalsgaard et al 2009) and interactions between parasites and their hosts (Kirk 1991, Poulin & Hamilton 1997, Sasal et al 1999, Johnson et al 2005. In a broad sense, the body size of any small 'associate' species -here defined as a species that is an obligate associate (e.g.…”

“…Bergmann's rule; see Blackburn et al 1999) that may mask or weaken host effects on parasite size (Randhawa & Poulin 2009). More recently, studies testing for positive cross-species size correlations between parasites and their hosts have corrected for shared phylogenetic history (Kirk 1991, Poulin & Hamilton 1997, Sasal et al 1999, Johnson et al 2005), a particularly important step as body size may be evolutionarily conserved in closely related associate lineages. Examining how size structures interactions between associates and their hosts in a phylogenetic context provides a unique opportunity to test the extent to which phylogenetic conservatism of associate size interacts with selection imposed by host size.…”